Abrading apparatus



Feb. 8, 1938. w. 1 KEEFr-:R

ABHADING APARATUS Original Filed July 25. 1935 2 Sheets-.Sheet l 3 wom/W04',

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Feb. 8, 1938. w. L. KEI-:FER

ABRADING APPARATUS 2 sheets-sheet 2 Original Filed July 25, 1935 JM? 4W Patented Feb. 8, 1938 2,108,006 ABRADING APPARATUS Walter L. Keefer, Hagerstown, Md., assignor to Pangborn Corporation, Hagerstown, Md., a. corporation of Maryland original application July 25, 1935, serial Ne. 33.-

185. Divided and this application June 26, 1937, Serial No. 150,648. Renewed November 15 Claims.

The present invention relates to abrading apparatus and it is more particularly concerned with mechanical abrasive projecting or propelling machines of the character wherein an abrasive is projected by centrifugal action against the work operated upon.

A primary object of the present invention is to provide a machine having all of the desirable characteristics of the successful abrading rnachine shown in copending application Serial No. '726,188 together with further highly desirable structural and operating features that improve the wearing qualities, life and efliciency of the mechanism materially. This application is a division of my application Serial No. 33,185, led July 25, 1935.

It is a major object of my invention to provide a novel centrifugal abrading machine that will eiiiciently utilize all of the abrasive supplied thereto, and have a long useful life in service, which is so constructedas to provide ready dis'- assembly for servicing, and yet which is low in cost.

It is a further object of my invention to provide a centrifugal abrading machine having impeller and propeller blades which are properly correlated to produce a uniform flow of abrasive to the propeller blades and to reduce the initial K impact of the abrasive therewith and the abrasive wear thereon, while improving the abrasive curtain discharged therefrom by increasing its concentration and reducing the stray abrasive discharge.

It is another object of this invention to provide a. novel abrasive feeding assembly forv centrifugalabrading machines in which the need for complicated and expensive air and abrasive seals is obviated.

A further object of this invention is to pro- V vide an abrasive feeding unit of novel design for abrading machines which may be readily removed from the machine as a unit without'disturbing any of the parts thereof.

My invention also aims to provide 'centrifugal abrading machines with an improved abrasive impeller assembly and generally to refine and improve other features of such machines.

Further objects of the present invention will become apparent as the detailed description thereof proceeds in connection with the annexed drawings, 4and from the appended claims.

In the drawings:

Figure 1 is a longitudinal sectional view of a centrifugal abrading machine embodying `my invention and it is taken-approximately on the line l--I of Figure 2.- In this view one of the propeller blade securing plates has been removed to show a part of the blade securing means.

Figure 2 is a sectional view taken substantially on the line 2-2 of Figure 1, and it shows one of the propeller blades in section. l

Figure 3 is a fragmentai sectional view through the impeller and feed assembly and the section is taken so as to intersect the impeller hub on the left-hand side of the figure, and to intersect the peripheral flange ofthe holder on the othe side of the figure.

Figure 4 is a right-hand end view (Figure 1) of the feeding cage with its `associated parts removed therefrom.

Figure 5 is a. fragmental top plan view of the bracket which holds the feeding assembly in position in the device shown in Figure 1.

With continued reference to 1 the drawings, wherein like reference ycharacters are employed to designate like parts throughout the several views thereof, the machine is supported upon a base designated generally at I0 and which provides an opening through which the blast wheel or runner assembly projects.

Mounted upon base I0 is a, runner wheel housing designatedl generally at H and which comprises end walls I2 and I3, side walls I4 and I5, and a cover I6 which is hinged to the housing in a manner to be presently described. Abrasive guard plates Il and i8 are secured to side walls I4 and I5 respectively, by means of nut and bolt assemblies I9. Base I 0 is provided with a member 20 having an opening filled with lead 20 or any other renewable material. A further reinforcing guard plate 2| is secured to plate I1 by means of a nut and bolt assembly 22. An abrasive guard plate 23 is also secured to the lower 28 having special dust proof or blind-ended nutsy 2s threaded thereon. Belts 2s htthreugn slots 30 in a pair of cross pieces 3l secured to lid I6, and are received with considerable clearance in lugs 32 secured to housing H so that nuts 29 need merely to be loosened and bolts 29 rocked out of slots 30 in cross pieces 3l to permit the lid to be lifted into opened position.

Secured to side wall`I2 of housing H by means of nut and bolt assemblies 33 and angle brackets 34, is an abrasive rebound guard 35 whose function will be pointed out hereinafter. A wear plate 36 is secured in place below the base in any suitable manner and 'carries an abrasive rebound guard 31.

- All of the rotatable parts of the machine are carried upona shaft 38, which may be mountedy for rotation in any suitable manner, but which is supported 1n the present instance by means of a pair of axially spaced bearings 39 which are provided with arms 4| for securing them to the base. As the shaft and bearing arrangement forms no part of the present invention, only one bearing assembly has been shown in order to simplify the disclosure.

Power may be applied to shaft 38 in any suitable manner and it extends into housing H through an opening dened by notches 42 and 43 formed respectively in base I0 and housing side wall l2. Supported on the shouldered end of shaft 38 is a heavy disc 45 and it is preferably keyed thereto in any suitable 'conventional manner. Disc 45 is restrained against axial displacement from shaft 38 by means of a plate 46 which bears against the end face of disc 45 and is secured to shaft 38 by two machine screws 41.

The abrasive propelling elements of my machine are carried by a rotatable runner head or rotor 48 which is secured to disc 45 by a plurality of counter-sunk screws 48. Runner 48 is provided with a peripheral flange 5| which operates to restrain the abrasive propelling blades against outward movement in response to centrifugal force. The abrasive propelling blades are preferably four in numberv and are designated gen'- erally ,at B. Blades B are secured in place in preferably symmetrical relationship on runner 48 in a manner similar to that employed in the aforesaid copending application, and with reference to Figures 1 and 2, four sector-shaped guide plates 53 are secured in place on head 48 by means of counter-sunk screws 54, and their edges are beveled so that adiacent sides of each pair of guide plates will form a, dove-tail groove. The side edge of each blade B is provided with a correspondingly beveled face 55, so that when blades B are inserted in the center of the machine and slid outwardly into position between the guide plates they will be firmly held against movement. Annular ange 5I prevents the blades from moving outwardly in response to centrifugal force and a bowed leaf spring 56, f1tting in a. groove 51 provided in each blade, frictionally restrains each blade against inward movement. As the blade restraining means forms no part of the present invention it will not 'be further described.

Referring to the configuration of the blades,

and with reference to Figures 1 and 2, each blade B is provided with a substantially fiat abrasive propelling surface 58, which extends from the outer end of the blade to a region near the inner end thereof. The inner end of each blade is preferably provided with a curved abrasive pick-up surface 6| for a purpose that will presently appear. With reference to Figure 1, each blade (in this instance' upper blade B) is provided with a pair of abrasive guidingV flanges 62 and 63. Flange 62 is substantially parallel to runner head 48 whereas flange 63 inclines toward the runner head at its outer end. Flange 63 is inclined in view of the fact that the velocity of the abrasive increases as it approaches the outer end of the blades and accordingly narrows down to a thinner stream. Hence the blade is wider at its inner end in order to insure th'at the abrasive will not escape laterally from the -blade as it is initially contacting therewith and is in a less contracted condition.

, Ihe mechanism I preferably employ for feeding abrasive into the space defined by the inner ends of the propelling blades will now bedescribed.

Bridging a semi-circular recess 66 provided in base I 0 is an arm or bracket 61 which is provided with a forwardly and-downwardly curving portion 68. Portion 68 is reinforced by means of a plurality of webs 10 which join it to arm 61. Arm 61 may be secured to base l0 in any suitable manner, but I preferably employ a pair of studs 69 which are secured in base l0 and which extend through open-ended slots 1| in arm 61. Nuts 12 are employed to hold arm 61 in place on base I0, and as seen in Figure 1 they are preferably provided with closed ends to exclude dust from the threads. Slots 1| are disposed with their open ends facing toward the rotor, so that when nuts 12 are loosened, bracket 61 may be slid to the right and removed.

In order to insure that arm 61 will be positioned properly when put in place over studsA 69, it is preferably provided with a pair of positioning set screws 14 for cooperation with studs 69, each having a locknut 15 turned thereon. To properly adjust positioning screws 14, arm or bracket 61- is put in place on base |0,\nuts 12 are taken up lightly, and arm 61 is then by experiment or measurement brought into the proper position. Nuts 12 are then taken up tight. Positioning screws 14 are then screwed up to take up the lost motion between them and studs 68, and locknuts 15 are then screwed into place to maintain the positioning screws in the proper set position. If desired, however, positioning screws 14 may be manipulated while nuts 12 are partially loosened and arm 61 is being maneuvered into proper position.

The forward face of the curved portion 68 of arm 61 is provided with a circumscribing flange 11 having vertical and horizontal portions. Secured to the forward face of portion 68 by three nut and bolt assemblies 19 and having a rabbeted portion 18 conforming to the flange of portion 68, is a holder 8|. Holder 8| provides a combined spout and cage or distributor support.

Holder 8| is accordingly stationarily but removably secured to base I0, and it is provided with a preferably integral spout portion 82 which has an overhanging lip 83 for cooperation with the impeller in a manner to be hereinafter pointed out. Spout portion 82 is provided with a funnel or spout extension 84, and although these parts may be integrally formed, I preferably form them in two pieces to facilitate casting of the parts. 'I'hey are fastened together by pairs of lugs 85 formed on the respective members and nut and bolt assemblies 86.

Abrasive introduced into spout 84 is conveyed into a cage or receptacle which is carried by holder 8|, and which is designated generally at C.

Cage C is provided with a generally cylindrical portion 81, a deep, preferably imperforate flange 88 and a shallower flange 8| in which four notches 88 are provided. Notch'es 89 correspond in number and spacing to the blades ofthe impeller, to be described hereinafter. Cage flange 9| vis piloted or centered upon a cylindrical hub or flange 92 provided on holder 8|. Cage C is also provided with a recessed face 83, and an element 84 covers 'slots 88 in holder 8|. erably adjustably supported for angular rocking movement about the axis of the machine upon `holder 8| in the following manner:

Preferably a pair of diametrically opposite studs 91 are secured in ang'e 8| of cage C and extend through apertures in slot cover 84. Studs 81 extend through arcuately-shaped slots 88 in holder 8|, as shown in Figure 3, and a pair of nuts 88 are turned thereon to releasably clamp cage C to Cage C is prefl holder 8|. As seen in Figure 1, nutsl 99 are of special form as their ends are closed to exclude dust and abrasive from the threads, and they provide hex manipulating heads which are disposed a considerable distance from cage C in 'order that the nuts may be readily loosened and manipulated during the cage adjusting operation. Nuts 99 also provide convenient operating handles which may be grasped for rocking cage C into proper angular adjusted position after they are loosened. Cage C is also provided with a discharge slot or opening |00, which inclines forwardly with respect to the direction of rotation of the runner, as seen in Figure 2.

I preferably employ an impeller or agitator i within cage C which rotates synchronously with runner 48, for insuring a proper feeding of lthe abrasive to the propeller blades B. The impeller or agitator is preferably equipped with the same number of blades as are present on runner 40,

- and in the present case they are four in number.

Impeller blades I| are joined' at one end by a cone-shaped cylindrical portion |02 providing a truncated cone-shaped internal abrasive feeding face, and into which lip 83 of spout 82 projects. Blades |0| are jointed at their other ends by a generally cup-shaped member preferably providing a circular abrasive baflling flange |03, and a deep cylindrical ange or hub |04 in which a pair of diametrically opposed slots |05 are formed.

`The impeller is preferably secured to the runner assembly by means of a long cap screw |06 which passes through an aperture in the central part of the impeller and plate 46; and is threaded into shaft 38. .Cap screw |06 pulls the impeller with its flange |04 into tight engagement with plate 46 and with its slots |05 embracing the heads of machine screws 41. By reason of slots |05 in the impeller flange fitting over screws 41, it is impossible to improperly assemble the impeller with the runner assembly, as these parts must be in alignment before cap screw |06 may be brought into its iinal tightened position. With reference to Figure 1, flange |03 ofthe impeller extendsv outwardly. beyond flange 88 of cage C, with the result that they are radially overlapped and abrasive leakage is minimized, because the abrasive in cage C would have to take a. tortuous path in order to escape therefrom. In order to minimize abrasive leakage over ange 9|, one wall |01 of each of slots 89 formed therein are beveled, and as seen in Figure 4 they are beveled in a direction to assist in maintaining the abrasive in cage C. l

Although I have termed blades B propeller blades, and blades I 0| impeller blades, their ac velocity to the abrasive prior to its being picked up by the propeller blades, and the latter function to impart the final abrading velocity to the abrasive, I have employed this terminology to differentiate these functions of the two sets of blades.

The impeller is assembled with theV runner assembly in a predetermined relationship to establish a highly important cooperation between the impeller blades and the propeller blades for feeding and propelling the abrasive in a novel manner. Referring to Figure 2, the direction of rotaltion of the runner is counter-clockwise and it is seen that each impeller blade |0I is disposed at a predetermined angle of advance in the direction of rotation of the runner with respect to its propelling blade B.n This relationship is established between the impeller and propeller blades sothat the abrasive which is churned around in cage C will be discharged through slot |00 a predetermined angle in advance of each bladeB. 'I'his synchronized or coordinated action of the impeller and propeller blades insures that the abrasive will; be positively thrown out into the path of the propeller blades, and-by reason of the angular velocity component of the abrasive, and the rearward inclination of the .inner ends of the blades, the abrasive is picked up with a minimum impact. This also results in a more restricted or contracted discharge from the wheel. Impeller blades |0| are also provided Withconcave faces I 'which face forwardly with respect to the direction of rotation of the runner assembly so that the abrasiveimpelled thereby will be confined to the width of the blades, and will accordingly be discharged through slot |00 onto blades B in a more contracted form. By confining outward ow of the abrasive over blades B to a narrower lateral area, less power is required to drive the Operation.

The work is placed under the machine opposite the discharge opening and it is to be understood that the work may assume various forms and may be moved in various ways while it is treated. For instance, the work may be located in a tumbling device or may be mounted on a truck to be moved about under the machine to expose various parts to the blast. Moreover, the work may be passed through a cabinet, and the machine mounted for oscillation about different axes in order to subject the vwork to the blast at various angles. Also, the Work may be passed through a. suitable cabinet or housing in strip or sheet form and subjected to the action of one or more of my machines. If desired, however, the machine may be mounted in inverted relationship in a cabinet to be directed against the lower side of the 1work passed therethrough or it may be mounted to discharge horizontally or at an oblique angle. The following discussion of the operation of the machine is therefore intended to apply to my machine irrespective of the manner in which the work is exposed to the blast stream.

Shaft 38 may be rotated at any suitable speed, but with a machine constructed as shown in the drawings, I nd that a speed of approximately 2500 R. P. M. in the direction indicated in Figure 4 is suitable for satisfactory operation of the machine. Cage C is mounted on holder 8| in the position shown in the drawings at the factory, and it has been found that with the proportions of the various parts as shown, and with the discharge opening |00 located as shown in Figure 2, the discharge from the machine will be properly located when the machine is rotated at the proper speed. Y

However, if it is found upon operating the machine that the discharge is not directed as desired, nuts 99 may be loosened and manipulated to rock cage C and thereby change the angular .relationship of abrasive discharge slot |00. As

the point at which the abrasive stream leaves the .wheel is determined by the point at which the `an abrasive of any suitable form, (preferably metal grit) is preferably allowed to drop by gravity into spout 84, and it is preferably metered as by means of -a screw or other conveyor operating at a predetermined constant speed. Rotation of runner head 48 causes blades B and impeller blades `|0| to establish a partial vacuum in the axially extending passage defined by the inner ends of the impeller blades and in the lower end' of spout 84, so that the abrasive entering the spout is picked up by a rapidly moving air stream and enters the impeller with a predetermined degree of initial velocity. The abrasive is then impelled outwardly over concave portions of the impeller blades, and when it reaches the blade tips it is churned around or agitated Within cage C. A dispersion of. air and abrasive which rotates forwardly with respect to the direction of rotation of the runner assembly is thereby established, and also a' stationary or slowly moving film of abrasive lodges on the interior of cylindrical portion 81 of cage C, and thereby protects it from excessive wear. Cage flanges 88 and 9| serve to confine the abrasive within the cage as it is being agitated.

The forwardly rotating dispersion of sand and air is of fairly uniform intensity but it isnaturally of somewhat more concentrated character immediately in front of the leading face |08 of each impeller blade. By reason of the angular advance of each impeller blade with respect to its corresponding propeller blade, the concentrated streams of abrasive on the leading faces of the impeller blades are thrown outwardly through slot |00 in such manner, and at such a time that the inner curved end 6| of blade B will properly pick them up with a minimum of impact and splash. As the abrasive is exhausted through slot |00, it possesses angular as well as radial velocity in view of the impelling-action of blades |0|. -This feature, when taken in connection with the fact that the inner ends of blades B are curved,`operates to minimize any abrading action that may take place as blades B initially pick up the abrasive.

as the tangential component of the velocity of an individual particle of abrasive is not greatly lower than the velocity of the inner ends of blades B, Wear of the latter is minimized.

As the abrasive is forwardly rotated in cage C under the influence of impeller blades |0| it is confined by flanges 88 and 9| and it will be seen The abrasive accordingly travels outwardly and angularly, and.,

velop due to the arrangement and location of the parts. It is accordingly unnecessary to provide anair or abrasive tight joint between the cage and thev holder. Y f

In view of the fact that disc 45 and runner head 48 are permanent parts, as distinguished from certain other parts of the device, which are frequently replaced and hence are replacement parts, `it is desired to completely protect these permanent parts againstabrasion. The end of disc 45 is protected by wear plate 46, which may be replacedin a manner to be hereinafter de scribed when it has become worn excessively by stray abrasive. The impeller and cage and blades B may likewise be replaced and in connection with blades B, it should be observed that as the abrasive travels outwardly over surfaces 59 of each blade, it is prevented from laterally escaping from the free edge of the blade by flange 63, and it is prevented from abrading runner head 48 or guide plates 53 by flange 62, which keeps the abrasive spaced a considerable distance from these parts.

The abrasive is therefore supplied to the inner ends of blades B in a predetermined limited angular region, and as it travels outwardly, each fore, none of the abrasive, properly discharged from the opening |00, strikes any of the stationary parts of the device. However, a minute amount of stray abrasive is sometimes admitted to the blades in a region other than that adjacent discharge slot |00, and this abrasive, as it is discharged from blades B (Figure 2) ,strikes either guard plate l1, 2 I, |-8 or 23. As the amount of this stray abrasive is comparatively small, the Wear plates accordingly have a long life before they must be renewed. When it does, however, become necessary to renew any of the housing guards or rebound guards they may be readily replaced by detaching their securing bolts.

Moreover, because of the large space provided between the tips of blades B and the upper part of the cabinet, particularly the corners of housing H, the abrasive is given a chance to expand and is not confined adjacent the rotor. Therefore wear of the rotor and the wear plates is minimized. Rebound guard 35 is provided in order to prevent stray abrasive from being discharged upwardly and striking guard plate 23 and then rebounding back into contact with and abrading 'runner head 40, which, as previously mentioned, is a permanent part of the machine. Lower rebound plate 31 is provided to prevent abrasive from rebounding from the work. and striking runner head 48. If it is desired to inspect the runner blades or other partsof the devicelocated in the upper portion of housing H, nuts 29 may be loosened and lid |6`lifted to expose the interior of the cabinet.

- When it becomes necessary to replace blades B it is merely necessary to loosen nuts 12, remove nuts 99, so as to detach cage C from the holder, and pull the entire feeding assembly (with the exception of Acage C) axially to the right, and remove it from the machine. It is then possible to reach into the comparatively large opening and remove the single cap screw |06 which holds the impeller in place and remove the impeller and cage C as a unit from the machine. After the impeller and cage have been removed from the machine they may be disassembled by aligning impeller blades |0| with notches 89 of flange 9|.

After cage C and the impeller have been removed in`the manner just described, blades B may then be individually slid inwardly to the large central space and then withdrawn and replaced by new blades. At this time, wear plate 46 may also be renewed, if necessary, by removing machine screws '41. After the new blades are in place and plate 46 is secured to shaft 38, the

impeller (or a new one if it requires replacement) is then put in place with cage C and the impeller and aligned with ,screws 41 as previously described. Although as illustrated I preferably employ the wear. plate 46 which is separately formed from the impeller because these parts wear at different rates of speed, they may if desired be made integral without departing from the spirit of the present invention. In the event that plate 46 and the impeller are integrally formed, screws 41 are dispensed with and dowel pins or the like employed to cooperate with openings in member 45 for properly positioning the impeller in the device, and also notches `89 will be formed in iiange 88 instead of flange 9|, in order to facilitate assembly of the impeller with the parts. Moreover, in the two part construction shown, notches 89 may be provided in flange 88 instead of'flangel, and in such case the entire feeding assembly, including cage C may be removed by merely loosening nuts 12 and aligning the impeller with notches, 89.

After the parts just described have been put in place, the remaining parts of the feed assembly may be slid to the'left toward the opening in the machine. The cage is then secured to the holder b-y nuts 99 and the holder assembly is slid over studs 69 until it is arrested by contact of positioning screws 14 with the studs. Nuts 12 are then tightened and the machine is ready for operation. In this connection it should be observed that the horizontal contacting bearing faces provided on bracket 61 and base Il are of considerable area, which forms an adequate support for the feed assembly.

Although I have illustrated and prefer to employ a runner assembly embodying four impeller blades and four propeller blades, it is to be understood that if desired the number of blades in each set may be one or more blades, depending upon the size of the wheel and the abrading characteristics desired. In any event, however, an equal number of blades is employed in each set, in order that the impeller may discharge the abrasive through slot |00 a predetermined angular degree in advance of the inner ends of the propeller blades and bring about the beneficial results previously discussed.` It is to be under- `stood, however, that insofar as the other novel features of my machine are concerned, an unequal number of impeller and 'propeller blades may be used without sacrificing the advantages of those features.

Although I have illustrated cage C as being adjustably mounted upon spout holder 8|, and I prefer to employ this arrangement as it makes it possible to maintain the spout in a fixed position irrespective of the adjusted position of the cage, it is to be understood that if desired these parts may be permanently connected or integrally formed, and arcuately-shaped slots provided in holder 8| or arm 68 in the region where bolt and nut assemblies 19 cooperate with them, so as to mount the holder as well as the cage for angular adjustment upon arm 68.

Although I have illustrated an impeller assembly that is disposed in a predetermined xed position by machine screws 41, andl I prefer to use this, construction, because I have experimented and determined the proper yangle of advance of the impeller blades with respect to the propeller blades, and which remains fixed throughout the life of the machine, it is to be understood that if it is desired to operate the machine in a manner that requires it, slots |05 in impeller flange |04 may be elongated so as to provide a predetermined range of adjustability of the impeller with respect to the runner, and the appended claims are intended to embrace my machine when it assumes this form. Moreover, I prefer to use the positioning means shown as it is of simple form and doesnot entail the use of additional-parts, but I may if desired, especially if an adjustable impeller is used, employ a dowel pin on one of the parts which may be selectively engaged with one, or with one of a plurality of holes located in another of the parts for positively or selectively adjusting the impeller respectively, without departing from the spirit of the present invention.

The terms runner and rotor employed in the appended claims are intended to embrace the blade carrying member irrespective of whether it is made in one piece or is as a matter of fact integrally formed with shaft 38, or is made up of two members 45 and 48 and secured to shaft 38 as shown in the drawings. Moreover, I prefer to support the propelling blades at one edge only, but it is to be understood that the invention embraces runner assemblies having an apertured side plate secured to the other edges of the blades or other similar constructions.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. .The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:-

1. In an abrading machine, at least one disclike member mounted for rotation, a plurality of abrasive propelling blades mounted on said member, means for feeding abrasive to said blades, means for rotating said member for propelling said abrasive at abrading velocities, and a stationarily supported. rebound abrasive guard mounted to one side of said member, one edge of said guard terminating in a plane normal to the axis of rotation of said member and passing through a region adjacent the junction of said member and said blades, said guard extending in an axial direction away from said blades.

2. The abrading apparatus described in claim 1, wherein said guard is of generally cylindrical configuration and is disposed closely adjacent and conforms to the outer periphery of said plate secured to said shaft and operable to protect a part of said runner and the end of said shaft against abrasive wear, said plate also being operable to preclude endwise displacement of said runner from said shaft. l

4. The abrading machine described in claim 3, together with an impeller disposed in said abrasive admitting space and secured to said runner for synchronous rotation therewith, said impeller bearing against said wear plate.

5. In an abrading apparatus an abrasive propelling head mounted for rotation and having a hollow abrasive admitting space adjacent its axis of rotation, an abrasive feeding device having a discharge end located in proximity to said abrasive admitting space for feeding abrasive thereto, a support providing a clamping face, holding means for releasably maintaining said feeding device in frictional engagement with said clamping face, and abutment means for adjustably limiting movement of said feeding device with respect to said rotor when said holding means is released, so as to properly locate said feeding device with respect to said abrasiveadmitting space.

6. 'Ihe abrading apparatus described in claim 5, wherein said holding means comprises at least one threaded element associated with said feeding device and support, and said abutment means comprises at least one threaded member mounted on said feeding device and operable to bear against said threaded element.

'7. In an abrading apparatus, a shaft mounted for rotation, a rotor mounted on said shaft and carrying a plurality of abrasive propelling blades which terminate short of the axis to define an abrasive admitting space, a wear plate covering the end of said shaft adjacent said rotor and secured to said shaft by at least two headed elements, an impeller disposed in said abrasive admitting space and abutting said wear plate, said impeller having a pair of recesses in which said headed elements nest, whereby said impeller is locked in a predetermined angular position onf; said wear plate, and means for clamping and maintaining said impeller in place against said wear plate.

8. The abrading apparatus described in claim '7, wherein said wear plateis provided with a generally circular recess and said impeller is provided with a generally circular base which seats in said recess and is piloted by the wallof said recess.

9. The abrading apparatus described in 7, wherein said impeller is provided withl an axially directed flange which abuts against said wear plate and said recesses are formed in said flange.

l0. The abrading apparatus described in claim 7, wherein said rotor is made in two parts which are detachably secured together, one of said rear face of said wear plate, the other of said parts surrounding the periphery of said wear plate and being provided with a surface disposed substantially ush with the front face of said Wear plate.

11. 'Ihe abrading apparatus set forth in claim 3, together with an impeller disposed in said abrasive admitting space and bearingagainst said wear plate for synchronous rotation therewith, said impeller and said wear plate having aligned central apertures, and a bolt extending through said apertures and being secured in the end of said shaft and having the head thereof bearing against said impeller and holding it in clamping engagement with said wear plate.

claim 12. In'an abrading apparatus, a shaft mounted for'rotation; a head having an axially extending opening therein, said head being concentrically mounted on said shaft with said shaft extending into said opening; a plurality of outwardly extending abrasive propelling blades mounted on said head and terminating short of the axis of rotation to define a central abrasive admitting space; a stationarily supported abrasive feeding device disposed .within said abrasive admitting space and operablev to feed abrasive over the inner ends of said blades; a centrally located wear plate closing said opening and protecting said shaft against abrasion; an impeller disposed in said abrasive feeding device and having a clamping face disposed in surface engagement with said wear plate; and means for releasably holding said impeller with said clamping face in engagement with said wear plate.

13. In an abrading apparatus, a hub having a central opening; a shaft tightly tting within said opening; a rotor comprising a disc mounted on said hub and having a central opening; a plurality of outwardly extending abrasive propelling blades terminating short of the axis of rotation to define a central abrasive admitting space; a stationarily supported abrasive feeding device disposed within said abrasive admitting space and operable to feed abrasive over the inner ends of said blade; a centrally located Wear plate mounted on said disc and closing the opening therein to protect said shaft against abrasion; an impeller disposed in said abrasive feeding device and having a clamping face disposed in surface engagement with said wear plate; and means for releasably holdingsaid impeller with said clamp.

ing face in engagement with said wear plate.

14. In an abrading apparatus, a rotor member of. disc-like form having a plurality of outwardly extending grooves defining guideways for a plurality of abrasive propelling blades, said member being provided with a central aperture and havinglmeans mounting itfor rotation; a wear plate mounted on said member and closing said opening and, disposed within the inner ends of said grooves, 'said blades terminating short of the axis of rotation to define a central abrasive admitting space; a hollow abrasive feeding device disposed in said space; and an impeller disposed in said feeding device and secured to said wear plate.

15. In' an'kabrading apparatus, a hub member having anjaxially extending opening provided therethrough, a: shaft tightly fitting within said opening, a rotor comprising a disc element having a central opening, means for securing said disc element to said hub member, said rotor having ma pluralitykof outwardly extending abrasive proparts surrounding said shaft and abutting the pelling blades terminating short of the axis of rotationpto define a central abrasive admitting space, afsjtationarily supported abrasive feeding device disposed within said abrasive admitting space and operable toA feed abrasive over the inner ends of said bla "a centrally located wear plate closing the ope r Y n said disc element so as to protect said shaf'tfagainst abrasion, said wear plate being recessed into said disc element so as to dispose it substantially flush with said disc element, means for releasably securing said wear plate in assembled position, an impeller disposed in said abrasive feeding device and means for releasably securing said impeller to said wear plate.

WALTER L. KEEFER.'

CERTIFICATE OF CORRECTION. Patent No 2,108,006., l February 8, 1958.

WALTER L. KEEFER. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 6, second column, line 50, claim l5, for 'the word "blade" read blades; and that the sai@ Letters Patent should be read with this correction therein that the same may conform to `the record of the case in the Patent Office.

signed and Sealed this 15th day of March, A. D., 1958.

Henry Van Arsdale, (Seal) Acting Cormissioner of Patents. 

